                    [:kPa :MPa] #(/ % 1000)
                    [:C :F] #(+ (* % 1.8) 32)
                    [:ft :m] #(/ (* % 30.48) 100)}]
+
     (converter [from to])))
 
 (defn typical-monitor-pressure [units]

        (keyword? arg)
        (repeatedly (fn [] (typical-injection-rate arg)))))

(defn typical-proppant-concentration
  ([]
   [:ppga (typical-proppant-concentration :ppga)])
  ([units]
   (cond (= units :ppga)
         (value-from-typical-range 0.2 10))))

(defn proppant-concentration-seq [arg]
  (cond (int? arg)
        (let [unit :ppga]
          [unit (take arg (proppant-concentration-seq unit))])
        (keyword? arg)
        (repeatedly (fn [] (typical-proppant-concentration arg)))))

        (repeatedly (fn [] (typical-surface-treating-pressure arg)))))

(defn rand-injection-rate-unit []
  (rand-nth [:bbl-per-min :bpm :m3-per-min :m3/min]))

(defn typical-injection-rate
  ([]
   (let [unit (rand-injection-rate-unit)]
     [unit (typical-injection-rate unit)]))
  ([unit]
   (cond (or (= unit :bbl-per-min)
             (= unit :bpm))
         (value-from-typical-range 75 100)
         (or (= unit :m3-per-min)
             (= unit :m3/min))
         (value-from-typical-range 11.92 15.9))))

(defn injection-rate-seq [arg]
  (cond (int? arg)
